Italian turns up in frightful uncool expression (8)
I believe the answer is:
locution
'expression' is the definition.
('locution' can be a synonym of 'expression')
'italian turns up in frightful uncool' is the wordplay.
'italian' becomes 'it'.
'turns up' says the letters should be written backwards.
'in' is an insertion indicator.
'frightful' indicates anagramming the letters (I've seen this in other clues).
'it' back-to-front is 'ti'.
'uncool' anagrammed gives 'locuon'.
'ti' placed inside 'locuon' is 'LOCUTION'.
(Other definitions for locution that I've seen before include "Style of speaking" , "manner of speaking" , "way of speaking" , "Person's style of speech" , "Style of speech or idiom" .)